1. Field of the Invention
This invention relates generally to adaptive cruise control systems for automotive vehicles, and more particularly to apparatus and methods for headway control.
2. Description of the Related Art
An adaptive cruise control (ACC) system can enhance performance of vehicle speed control, also known as vehicle cruise control, by allowing a vehicle to actively track and follow a target vehicle while maintaining a follow distance that is proportional to the timed headway between the vehicles plus some minimum distance. The speed of the follow vehicle is controlled by controlling the application of acceleration force to the vehicle over a range spanning positive and negative accelerations.
Positive acceleration, sometimes in context simply called acceleration, may be controlled via an electronic-actuated mechanism that exercises control over an engine or motor that propels the vehicle. A vehicle propelled by an internal combustion engine may have an electronic throttle control that controls the amount of engine throttle opening to thereby apply a corresponding acceleration force to the vehicle via a drivetrain of the vehicle.
Negative acceleration, sometimes called deceleration, may be applied to a vehicle via service brakes of the vehicle. In a vehicle that has hydraulic-actuated service brakes at wheels of the vehicle and an ABS system for operating the vehicle's service brakes, an adaptive cruise control may apply deceleration force to the vehicle via the ABS hydraulic system.
Various arrangements for adaptive cruise control are shown in various patents, including one or more of U.S. Pat. Nos. 5,053,979; 5,396,426; 5,400,864; 5,454,442; 5,493,302; 5,594,645; and 5,629,851.